Overhead reduction in frequency division duplexing (FDD) multiple-input multiple-output (MIMO)

1. A first wireless device comprising: processing circuitry configured to: determine first beam information based at least in part on second beam information received from a second wireless device via device-to-device communications, the first beam information indicating a first beam selected by the first wireless device for downlink wireless communications, the second beam information indicating a second beam selected by the second wireless device for downlink wireless communications, wherein the first beam information and the second beam information correspond to respective precoding matrix indicators, wherein the determination of the first beam information is based at least in part on third beam information received from a third wireless device via device-to-device communications, the third beam information indicating at least one beam selected by the third wireless device for wireless communications, and wherein a grid of beams precoder is based at least in part on the third beam information; and cause transmission of the first beam information for grid of beams precoder determination.

2. The first wireless device of claim 1, wherein the first beam information includes at least one of an effective covariance, a rank indication and index of beam codebook.

3. The first wireless device of claim 1, wherein the determination of the first beam information is based at least in part on a selection criteria that includes at least one of: a minimum channel gain associated with a beam; avoidance of multi-user interference compared to at least one other beam; maximize signal-to-interference noise ratio compared to at least one other beam; and a reduced in beam training overhead compared to at least one other beam.

4. The first wireless device of claim 1, wherein the processing circuitry is further configured to: receive at least one precoded training sequence that is based at least in part on the grid of beams precoder, the grid of beams precoder being based at in part on the first beam information and second beam information; estimate an effective channel between the first wireless device and a network node based at least in part on the received at least one precoded training sequence; and report the estimated effective channel to the network node for Multiple-Input Multiple-Output (MIMO) data precoder determination.

5. The first wireless device of claim 4, wherein the receiving of the precoded training sequence and the reporting of the estimated effective channel are performed during a predefined channel coherence time period.

6. The first wireless device of claim 5, wherein the first beam information is determined during a predefined beam coherence time period different from the predefined channel coherence time period.

7. A method implemented by a first wireless device, the method comprising: determining first beam information based at least in part on second beam information received from a second wireless device via device-to-device communications, the first beam information indicating a first beam selected by the first wireless device for downlink wireless communications, the second beam information indicating a second beam selected by the second wireless device for downlink wireless communications, wherein the first beam information and the second beam information correspond to respective precoding matrix indicators, wherein the determination of the first beam information is based at least in part on third beam information received from a third wireless device via device-to-device communications, the third beam information indicating at least one beam selected by the third wireless device for wireless communications, and wherein a grid of beams precoder is based at least in part on the third beam information; and causing transmission of the first beam information for grid of beams precoder determination.

8. The method of claim 7, further comprising: receiving at least one precoded training sequence that is based at least in part on the grid of beams precoder, the grid of beams precoder being based at in part on the first beam information and second beam information; estimating an effective channel between the first wireless device and a network node based at least in part on the received at least one precoded training sequence; and reporting the estimated effective channel to the network node for Multiple-Input Multiple-Output (MIMO) data precoder determination.

9. A network node in communication with a plurality of wireless devices, the network node comprising: processing circuitry configured to: receive first beam information from a first wireless device of the plurality of wireless devices, the first beam information being based at least in part on second beam information associated with a second wireless device of the plurality of wireless devices, wherein the first beam information and second beam information corresponds to respective pre-coding matrix indicators; receive the second beam information from the second wireless device; determine a grid of beams precoder based at least in part on the first beam information and the second beam information; and during a coherence time, alternate between training phase and data communication phase, the training phase includes receiving precoded training sequences and reporting an estimated effective channel based at least in part on the precoded training sequences, and the data communication phase includes receiving data symbols associated with a data precoder based at least in part on the reported estimated effective channel.

10. The network node of claim 9, wherein the first beam information includes at least one of an effective covariance, a rank indication and index of beam codebook.

11. The network node of claim 9, wherein the first beam information is based at least in part on a selection criteria includes at least one of: a minimum channel gain associated with a beam; avoidance of multi-user interference compared to at least one other beam; maximize signal-to-interference noise ratio compared to at least one other beam; and a reduced in beam training overhead compared to at least one other beam.

12. The network node of claim 9, wherein the processing circuitry is further configured to: cause transmission of at least one precoded training sequence that is based at least in part on the grid of beams precoder; receive an estimate of an effective channel between the first wireless device and the network node that is based at least in part on the at least one precoded training sequence; receive a report of the estimated effective channel; and determine a Multiple-Input Multiple-Output (MIMO) data precoder based at least in part on the report of the estimated effective channel.

13. The network node of claim 12, wherein the transmission of the precoded training sequence and the receiving of reporting of the estimated effective channel occur during a predefined channel coherence time period.

14. The network node of claim 9, wherein the first beam information is based at least in part on third beam information associated with a third wireless device, the third beam information indicating at least one beam selected by the third wireless device for wireless communications.

15. The network node of claim 14, wherein the processing circuitry is further configured to receive the third beam information from the third wireless device; and the grid of beams precoder being based at least in part on the third beam information.

16. A method implemented in a network node that is in communication with a plurality of wireless devices, the method comprising: receiving first beam information from a first wireless device of the plurality of wireless devices, the first beam information being based at least in part on second beam information associated with a second wireless device of the plurality of wireless devices, wherein the first beam information and the second beam information correspond to respective precoding matrix indicators; receiving the second beam information from the second wireless device; determining a grid of beams precoder based at least in part on the first beam information and the second beam information; and during a coherence time, alternating between training phase and data communication phase, the training phase includes receiving precoded training sequences and reporting an estimated effective channel based at least in part on the precoded training sequences, and the data communication phase includes receiving data symbols associated with a data precoder based at least in part on the reported estimated effective channel.

17. The method of claim 16, further comprising: causing transmission of at least one precoded training sequence that is based at least in part on the grid of beams precoder; receiving an estimate of an effective channel between the first wireless device and the network node that is based at least in part on the at least one precoded training sequence; receiving a report of the estimated effective channel; and determining a Multiple-Input Multiple-Output (MIMO) data precoder based at least in part on the report of the estimated effective channel.